SEVERE: java.lang.OutOfMemoryError: Java heap space

[rm_solr]

Occasionally when inserting I get the error message
 SEVERE: java.lang.OutOfMemoryError: Java heap space
Any clues how to track down when&where it's happening?
Or any good way I can get better clues how to track it down?

I'm doing inserts of about 1000 documents at a time between
commits.  Would doing a smaller number avoid this problem.
Or, better - any way I can calculate how many docs I can
insert in a batch without triggering this?

A concise way to get just IDs

[rm_solr]

Is there a consise way to query just a single field
from a solr query?

I was trying to use solr in a BI application which
will allow the dynamic creation of olap cubes based
on the results of keyword searches; and in this case
I'm not really interested in just the top N results
nor the documents themsleves; but rather just the
complete list of IDs that match.

With the queries I know how to write, I get responses
like this:
=

00

 
  644960
 
 
  13
 
 .. and 200,000 or so more lines..


=


I was extremely pleased to see that Solr itself seems
fast enough to be useful, but found that I'm spending
a dissapointing amount of time sending the results through
an XML parser that's surely overkill for this task.


Are there any options where I could get a result
that looks something like
=

00

 
  644960 13 8357 66772 193162 
  . and 60,000 or so more numbers separated by whitespace.
 


=

Or should I be looking for an altogether different way of
approaching things?

   Thanks,
   Ron M